I think this is a complicted question, and every situation is going to be different.
Some guidelines in making the decision:
1) Figure out what went wrong in the first marriage. It is entirely possible, and quite common, to keep being attracted to people with the same set of problems - some women fall for charming abusers over and over, some are drawn to fun but irresponsible men. before committing a second time, be sure she resolved the issues that led to the first marriage ending.
2) Be clear with the new spouse-canidate about obligations she has to others. If a new husband is willing to accept the fact that she has ailing parents (we probably all will at some point) that should be no barrier to marriage. If he has assumptions her other obligations will take a back seat to him - that needs to be up front.
3) Is she simply in love, or is this real marriage material? Being in love is lovely, but you need alot more compatibility, plus shared goals in life to take a romantic relationship to the marriage level. Maybe just having a romance is what she really wants right now. She doesn't have to get married every time she falls in love.
4) Take time. Sounds like she has a complicated life. You know what they say,"Marry in haste, repent at leisure."